It is counted as belonging to the state of the art, to provide electric motors with cooling ribs over the complete periphery of their motor housing, in order to lead away waste heat occurring in the electric motor on operation, wherein these cooling ribs are arranged more or less parallel to the longitudinal axis of the motor and are to lead away the motor heat by way of convection cooling. This is often encouraged by a fan wheel which is seated on the motor shaft and which axially sucks air via a fan cowl and then leads it along the cooling ribs, in order in this manner to lead away the waste heat of the motor via this airflow.
In the meanwhile, with increasingly smaller power electronics, electric motors, in particular for drive of centrifugal pumps, which in the terminal box provided on the electric motor and initially serving exclusively for the electrical connection of the motor, contain electronic circuits and in particular also power electronics, typically those of an electronic speed controller for the motor, have established themselves. The terminal box thereby with modern motors simultaneously forms an electronics housing. However, the waste heat of such power electronics used today lies in a magnitude to that of the motor waste heat, which is why it is counted as belonging to the state of the art, to not only provide the electric motor itself with cooling ribs, but also the terminal box, thus the electronics housing located therein. Thereby, it has been found to be advantageous to likewise let the cooling ribs of the electronics housing run in the longitudinal direction of the motor, thus parallel to the longitudinal ribs of the motor, in order thus to also cool the electronics housing with the cooling airflow of the motor.
With modern permanent magnet rotors, the waste heat of the motor due to the comparatively good efficiency is significantly lower for example than with asynchronous motors or direct current motors. With this, the cooling requirement, in particular with motors controlled by speed controller, shifts from the motor housing to the electronics housing. The cooling ribs are dimensioned in a smaller manner in accordance with the reduced cooling requirement of the motor, which however tends to be somewhat disadvantageous for the cooling of the electronics housing.